Hydrometer Calibration Temperature.

Not all hydrometers are the same, they are very sensitive instruments specifically designed to be accurate at a specific known temperature. For this reason it is important to know the temperature at which you take a reading from your Hydrometer and also the temperature that the Hydrometer is calibrated for.

Your Hydrometer should have the calibration temperature printed on it somewhere similar to the picture below.

Click image to enlarge.

Hydrometers are usually calibrated to 20 degrees Celsius although for a lot of older Hydrometers, a calibration temperature of 15 degrees is not uncommon.

Starting and Final Gravity

For a detailed explanation of how to collect the Starting and Final Gravity readings, see the How to use a Hydrometer page.

Starting and Final Temperature Readings

The temperature of the liquid that you are measuring. Fortunately, if the temperature is fairly stable in the room where you store your fermenter, in most cases you can just use the temperature from the thermometer on the side of the fermenting drum.

If the room temperature tends to fluctuate so that the temperature of the liquid in the test jar may be different to that of the main fermenter drum, simply buy a cheap thermometer and take the temperature of the liquid just after you remove the hydrometer from the test jar.

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